It has already been proposed to pickle, clean and polish metal strip and wires using ultrasonic wave energy in a treating solution which may be an acid, a detergent or a liquid with abrasive particles suspended in the liquid. Examples of prior art U.S. patents in this field are Englehart U.S. Pat. No. 2,894,860, Osterman et al U.S. Pat. No. 3,066,084 and Sasaki U.S. Pat. No. 3,240,963.
It has also been proposed to utilize the reflection characteristics of ultrasonic wave energy to treat objects in treating solutions where the energy is reflected from tank surfaces and the surface of the treating solution. Examples of prior art U.S. patents of this category are Branson U.S. Pat. No. 2,987,068, Hightower U.S. Pat. No. 3,033,710 and Kouril U.S. Pat. No. 3,433,669.
Further it has been proposed to use heavy granite tanks for pickling as described in U.S. Patent to White et al, U.S. Pat. No. 3,473,791.
It is now well known that highly efficient ultrasonic wave energy generators produce a beam of wave energy with only slight divergence, for example 5%, and thus that the effect of the beam of wave energy in a treating solution on objects in its path is localized. It follows that effective treatment of a strip of metal moving through a treating solution with ultrasonic generators directed toward the strip and relying only on direct action of the beam of energy would require an economically prohibitive number of generators. Such use of ultrasonic generators or transducers also runs into problems of standing waves which reduce or even render ineffective the desired action of the ultrasonic energy. Even where reflection of the generated beam of ultrasonic wave energy has been contemplated, attenuation of the energy in the beam by long paths through a treating solution has reduced the effectiveness of such arrangements. As a result the ultrasonic treatment of moving strips of metal has not progressed in industry to the extent that might be expected.
The shortcomings of the prior art practices have been removed or alleviated in the present invention.